1. Field of the Invention
The invention is directed to an improved electrohydraulic brake system for a vehicle.
2. Description of the Prior Art
A brake system of the type with which this invention is concerned has already been disclosed, for instance in German Patent Disclosure DE 196 36 432 A1. This known brake system has a muscle-force-actuatable auxiliary brake and an external-force-actuatable service brake. For switching the brake system over from the service braking state to the auxiliary braking state, such brake systems have operating mode switchover valves, which are triggerable by an electronic control unit. Moreover, for simulating the pedal travel in the service braking state of the brake system, in which a pressure medium connection between a master cylinder and a wheel brake is interrupted by the aforementioned operating mode switchover valves, there is a piston/cylinder unit which receives the volume of pressure medium positively displaced in the master cylinder by the actuation of the brake pedal by the driver's foot. The piston/cylinder unit can be hydraulically blocked in the auxiliary braking state of the brake system, so that the volume of pressure medium positively displaced in the master cylinder is available to the greatest possible extent for building up pressure at the wheel brakes. The valves for switching over between the two modes of operation of the brake system and the blocking valve of the piston/cylinder unit are embodied separately. This increases the number of existing components as well as the effort and expense of assembly and the installation space required. Finally, the number of potential sources of error increase, as do costs.